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Fraser
2007-May-31, 06:56 PM
One of the brightest, closest stars to the Earth is Altair, located about 15 light-years away. For the first time, astronomers have imaged its surface, getting a better look at this bizarre neighbour. ...

Read the full blog entry (http://www.universetoday.com/2007/05/31/astronomers-see-the-face-of-altair/)

Doctor Know
2007-Jun-01, 01:50 AM
Altair is ovoid? I had no idea. That'd be a hard sun to eclipse. ;)

Darrrius
2007-Jun-01, 01:10 PM
So if it was "Imaged" - how come we have this artists impression instead of the photo?

Palomar
2007-Jun-01, 01:14 PM
:eh: So...Altair's another "bullet star" like Regulus?

Yes, I'm also wondering why an artists' impression instead of an actual image.

Mansie
2007-Jun-01, 02:05 PM
This artists impression has appeared on news sites all around the world - and I'm sure it'll be in the newspapers tomorrow. I followed the links and could still find no original images. Where are they? and are the surface details accurate? I still have no idea what it is we are looking at.

Hamlet
2007-Jun-01, 02:21 PM
Here is a link to the Altair 2007 Resource Page (http://www.astro.lsa.umich.edu/~monnier/Local/altair2007.html) at the University of Michigan that has a couple of images from the CHARA interferometer.

John Mendenhall
2007-Jun-01, 04:12 PM
Here is a good link with a high-resolution image available:

http://www.nsf.gov/news/news_images.jsp?cntn_id=109612&org=OLPA

What a picture! How about doing Betelgeuse? Should be able to see sunspots (Betelspots?)

George
2007-Jun-01, 07:45 PM
Simply amazing!!! Wouldn't they have better resolution, though, using optical imaging instead of IR?

[I would have guessed the coloring would have been just the opposite, blue where the white is, and white, or lighter blue, where the blue is shown. But, this is not just a CLV issue, no doubt.]

parallaxicality
2007-Jun-01, 08:35 PM
Is that CHARA image in the public domain? Wikipedia could use it.

dhd40
2007-Jun-01, 08:38 PM
Here is a good link with a high-resolution image available:

http://www.nsf.gov/news/news_images.jsp?cntn_id=109612&org=OLPA

What a picture! How about doing Betelgeuse? Should be able to see sunspots (Betelspots?)

Would be nice, indeed. Unfortunately, Beteigeuze´s (Betelgeuse´s) distance is appr. 400 LYs, whereas Altair´s distance is only 15 LYs.

By the way, is there an international *star-name-standard*?

Nick4
2007-Jun-06, 05:43 AM
Altair is ovoid? I had no idea. That'd be a hard sun to eclipse. ;)

Oh that made me laugh...lol that was funny good one

Nick4
2007-Jun-06, 05:43 AM
thats a cool pic of that star...is it really that color cuz thats the coolest blue iv ever seen.

George
2007-Jun-06, 01:31 PM
thats a cool pic of that star...is it really that color cuz thats the coolest blue iv ever seen.
The image is from an artist, but it might actually look that blue if you used a special neutral filter to reduce the star's intense brilliance.

eburacum45
2007-Jun-06, 04:36 PM
Simply amazing!!! Wouldn't they have better resolution, though, using optical imaging instead of IR?

[I would have guessed the coloring would have been just the opposite, blue where the white is, and white, or lighter blue, where the blue is shown. But, this is not just a CLV issue, no doubt.]

Surely the coolest colours would be at the equator, so the poles would be bluer and the equator would be yellower, depending on the average temperature of the star.

Here is a video I've made of Regulus in Celestia, showing the gravity darkening effect as I see it (please let me know if it's wrong)
http://www.youtube.com/watch?v=g_ZFkyrYgZA

George
2007-Jun-06, 05:36 PM
Surely the coolest colours would be at the equator, so the poles would be bluer and the equator would be yellower, depending on the average temperature of the star. Yes, that is what I would expect, too. However, I would say whiter in lieu of yellower due to the exteme surface temp. Notice that the depiction is more the opposite, white is not at the equator but at the pole. This seems opposite of what it might look like, assuming no surface distrubance. Yet, it may be a surface disturbance that is the key issue, perhaps.


Here is a video I've made of Regulus in Celestia, showing the gravity darkening effect as I see it (please let me know if it's wrong)
http://www.youtube.com/watch?v=g_ZFkyrYgZA Wow. [I wish I had time to learn that stuff.] I would expect it would be a blue-white star, however, but more white at the equator. [I like its peculiar motion (in both uses of the word) at the end of the video. :)]

eburacum45
2007-Jun-07, 03:46 PM
Well, I'll try making an alternate texture with a blueish polar region and white equator; but the way these models work, that will probably make the poles look darker and the equator brighter. In an emissive model the white regions are always the brightest, as one might expect. The only way to avoid this is to make the poles blue and the equator a light grey, which might look a little odd. What is needed, but is not yet available in this program, is high dynamic range lighting effects, which could make the poles look much brighter even if they were blue.

George
2007-Jun-07, 05:08 PM
Well, I'll try making an alternate texture with a blueish polar region and white equator; but the way these models work, that will probably make the poles look darker and the equator brighter. In an emissive model the white regions are always the brightest, as one might expect. The only way to avoid this is to make the poles blue and the equator a light grey, which might look a little odd. It is a little surprsing you are limited in color selection. White is very dominate in stellar color because blackbodies emit the full spectrum of colors.

Interestingly, if we allow the idea of bb distribution for stellar cores (at least for the visible portion of the spectrum), their emission in the visible band is a 4th power distribution, which is also true in Rayleigh Scattering (like our sky). Thus, with a heavy-duty flux attenuator (and capacitor, no doubt ;)), cores would look sky blue, I think.

Is there a known physics reason why our atmosphere would scatter light the same as it would emit light (visible) at 15 million K? [You don't have to elaborate, just nod your head. :) ]

eburacum45
2007-Jun-07, 06:00 PM
It is a little surprsing you are limited in color selection. White is very dominate in stellar color because blackbodies emit the full spectrum of colors.
It's not so much that one is limited for colours in Celestia; the full range of colours can be displayed. It is just that, on a PC monitor, white is the brightest colour; if you want to have a blueish colour which is brighter than white you need to introduce a bluish glare effect, something which Celestia can't do at the moment.

Using a Spinal Tap analogy, white is 10; to have a blue colour which is brighter than white, you have to turn it up to 11.

I can do this in post-processing, but not easily in a moving image. So for that clip, I just transposed the spectrum down an octave or so, so that blue became white, and white became yellow. Perhaps the eye-brain interface might do something similar if we were actually in Regulus orbit.

eburacum45
2007-Jun-07, 06:29 PM
The CHARA people have seen fit to produce this image of Altair as well as the blue one, which in my opinion is more representative (although probably much too cool).
http://www.astro.lsa.umich.edu/~monnier/Local/Altair_files/PR_image1crop.jpg

George
2007-Jun-07, 09:00 PM
It's not so much that one is limited for colours in Celestia; the full range of colours can be displayed. It is just that, on a PC monitor, white is the brightest colour; if you want to have a blueish colour which is brighter than white you need to introduce a bluish glare effect, something which Celestia can't do at the moment. Ok, I see your problem. The blue should actually be brighter since it is all the white plus extra blue (and some green) photons. Would a slight gray work for the white, similar to a K factor in CMYK color?

What would really be cool is if you can make the rotating disk along the equator appear white (slight gray?), but maintain a bluish-white for the central region. This would present what I think exists in stars due to the center-to-limb variation in temperature. In the center, we can see down to the bottom of their photospheres.


Perhaps the eye-brain interface might do something similar if we were actually in Regulus orbit. Maybe, but I doubt it. The retinex (for retina-cortex) may not be that erroneously affected by a radiating sphere cast in a black background.